Cell Membranes 3 Flashcards
Why can water more freely between extracellular and intracellular fluid?
Aquaporins
What are cell membranes in terms of permeability?
Selectively permeable. What crosses depends on the properties of the cell membrane (lipid and protein) and substance (size and lipid solubility)
What is Diffusion?
The movement of molecules from and area of HIGH concentration to LOW concentration
Factors that speed up diffusion across a membrane
-membranes surface area is larger
-membrane is thinner
-concentration gradient is larger
-membrane is more permeable to the molecule
What law: Surface area x concentration gradient x membrane permeability
Fick’s Law of Diffusion
What is Protein Mediated Transport
-majority of molecules in the body are either lipophobic or electrically charged and can’t cross the membrane by diffusion
What are Channels Proteins made of?
Large membrane spanning protein subunits that create a cluster of cylinders with a pore through the middle
Gated Channels
Normally closed
-chemically gated (ligand)
-voltage gated
-mechanically gated
How are channels proteins determined
Selectively by the size of pore and the charge of the amino acids lining the pore
What are carrier proteins?
Large complex proteins that change conformation to move molecules
-can move small organic molecules that can’t pass through channels
What is Facilitated Diffusion?
Ions move down their concentration gradient, doesn’t require energy (passive), uses channels or carrier proteins
What is Active Transport
Moves molecules against their concentration gradients from an area of low concentration to an area with high concentration
-requires energy and uses carrier proteins
2 Types of Active Transport
Primary and Secondary
What is Primary Active Transport
Energy to move molecule comes directly from hydrolyzing ATP
What is Secondary Active Transport
Uses the potential energy stored in the concentration gradient of one molecule to push another molecules against their concentration gradient
